The cold tongue mode (CTM) is the second EOF mode of sea surface temperature anomaly (SSTA) variability over the tropical Pacific and represents the out- of- phase relationship in SSTA variability between the Pacific cold tongue region and elsewhere in the tropical Pacific. A positive CTM is characterized by cold SSTA in the Pacific cold tongue region and warm SSTA in the rest of the tropical Pacific, with conditions reversed for a negative CTM. The CTM is a coupled air- sea mode, and its long- term variability is most probably induced by ocean dynamical processes in response to global warming [ Zhang et al., 2010]. This study focuses on the specific ocean dynamical processes associated with the CTM and its possible relationship with global warming. A heat budget diagnosis of ocean temperature in the eastern equatorial Pacific shows that the net heat flux plays a damping role and the four ocean advection terms (2u0@ T =@ x, 2 v@ T0=@ y, 2 w@ T0=@ z, and 2w0@ T =@ z) contribute to the temperature change associated with the CTM. Among them, the vertical advection of the anomalous temperature by the mean upwelling (2 w@ T0=@ z) makes a dominant contribution to the long- term change in the CTM. The long- term change of the term 2 w@ T0=@ z is controlled mainly by the decreasing vertical gradient of the ocean temperature anomaly (@ T0=@ z). The other three advection terms make a minor contribution to the long- term change in the CTM.